SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
iperf - A TCP, UDP, and SCTP network bandwidth measurement tool
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
netperf - Netperf is a benchmark that can be used to measure the performance of many different types of networking. It provides tests for both unidirectional throughput, and end-to-end latency. - HewlettPack...
Packet Sender - Packet Sender can send and receive UDP, TCP, and SSL on the ports of your choosing.
TamoSoft Throughput Test - TamoSoft Throughput Test is a utility for testing the performance of a wireless or wired network.